First, that in the lower grade the reproductions themselves seem merged in those of irritability, from the very circumstance that the latter constitutes no pole, either to the former, or to sensibility. The force of irritability acts, therefore, in the insect world, in full predominance; while the emergence of sensibility in the fish calls forth the opposite pole of reproduction, as a _distinct_ power, and causes therefore the irritability to flow, in part, into the power of reproduction. The second result of this ascent is the direction of the organizing power, _ad intra_, with the consequent greater simplicity of the exterior form, and the substitution of condensed and flexible force, with comparative unity of implements, for that variety of tools, almost as numerous as the several objects to which they are to be applied, which arises from, and characterises, the superficial life of the insect creation. This grade of ascension, however, like the former, is accompanied by an apparent retrograde movement. For from this very accession of vital intensity we must account for the absence in the fishes of all the formative, or rather (if our language will permit it) _fabricative_ instincts. How could it be otherwise? These instincts are the surplus and projection of the organizing power in the direction _ad extra_, and could not, therefore, have been expected in the class of animals that represent the first intuitive effort of organization, and are themselves the product of its first movement in the direction _ad intra_. But Nature never loses what she has once learnt, though in the acquirement of each new power she intermits, or performs less energetically, the act immediately preceding. She often drops a faculty, but never fails to pick it up again. She may seem forgetful and absent, but it is only to recollect herself with _additional_, as well as _recruited_ vigour, in some after and higher state; as if the sleep of powers, as well as of bodies, were the season and condition of their growth. Accordingly, we find these instincts again, and with them a wonderful synthesis of fish and insect, as a higher third, in the feathered inhabitants of the air. Nay, she seems to have gone yet further back, and having given B + C = D in the birds, so to have sported with one solitary instance of B + D = A in that curious animal the dragon, the anatomy of which has been recently given to the public by Tiedemann; from whose work it appears, that this creature presents itself to us with the wings of the insect, and with the nervous system, the brain, and the cranium of the bird, in their several rudiments.